Filler Compatibility with Topcoat

A finisher finds that some varnishes pull out the vinyl spackling he's been using for to fill holes and grain. Others share ideas for solving the problem. December 31, 2005

I have been spraying lacquers for many years now, but I have just started spraying conversion varnishes. When I am prepping wood to be topcoated with a pigmented lacquer, I first use a regular wood filler (Famowood) to fill any cracks and holes that I can see. Next, I spray on my first coat of primer and then sand the primer, then spray on my second coat of primer. Then I fill any cracks and holes that I couldn't see prior to priming with vinyl spackling. Then, I sand the second coat of primer along with the spackling and topcoat with the pigmented lacquer. Everything is fine.

The problem I am having now is that when I spray ML Campbell's Resistant over the spackling, it wrinkles and lifts the spackling back out of the holes. With the varnish, I spray two coats of Clawlock catalyzed primer, sanding in between each coat. Then I do my final filling with the spackling and sand that. Next, when I spray the resistant, it causes problems with the spackling. Do you know of something else that I could use in place of the spackling to do a final fill before the topcoat? A Campbell tech told me to fill everything prior to priming. I told him that no matter how much filling you do prior to priming, you can't see everything until you put that primer on. Then any little cracks or holes show up. Any advice on what I can use as a final fill prior to applying the resistant would be greatly appreciated.

Forum Responses
(Finishing Forum)
I fill with filler sand whatever I can see, then two base coats, followed with topcoat. Whatever defect I could not see, I correct after that with colored wax figures, and this does a great job with no problem. Why should you do it in between?

Why don't you prime, fill, prime? Then the resistant shouldn't pull out the spackle.

I don't think I actually invented this, but I haven't heard of anybody else doing it. I use "fat" primer (left over catalyzed primer that's thickened) as filler on primer. It melds completely with the primed surface. I've never tried this with Clawlock, but it works great with Unisurfacer.

Fill knots and holes with wood filler. Sand. Prime. Fill any little cracks or holes that show up with fat primer. Sand. 2nd coat primer. Topcoat within 4 hours so you don't have to sand again.

Bonus is there's no sanding scratches to telegraph through the topcoat.

From the original questioner:
Thank you to all who have responded. I will take your advice and give it a try.